The present invention generally relates to turbines and more specifically to rotors used in turbine applications.
Since the earliest use of water to turn a wheel, turbines have provided needed mechanical action for myriad functions. In modern times, turbines are used to generate electricity, power jet aircraft and increase the power of automobiles using turbochargers. Many turbine applications use two rotors on the same shaft so that one turbine powers the other. When the rotors are on a fairly long connecting shaft problems of balance, shaft whip, and multiple vibrational modes become worse. These can cause various problems up to the failure of the machine.
Smaller turbine engines are now being used for local power generation applications as backup power and for peak shaving. The U.S. Department of Energy (DOE) is planning to use similar smaller turbines for distributed energy generation in homes. In these smaller turbines, the turbine blades are not cooled so the turbine entrance temperatures must be more severely limited to avoid damage. However, in general, the higher the turbine inlet temperature of a turbine engine, the more efficient it is. Therefore, the efficiency of a turbine engine is determined by the ability of the turbine""s nozzles and blades to withstand the heat of the exhaust gases that pass through them.
In larger turbines, it is not unusual to find that approximately one-third of the air moved through them is used for cooling nozzles and blades and not for power production. Prior research has concentrated on developing materials that can withstand higher temperatures for use as turbine parts. However, these higher temperature materials generally are rare and quite expensive. Other research has been in the area of schemes for cooling the components. Likewise, these schemes are costly and inefficient. Present turbine engines of all sizes do not operate anywhere near the theoretical maximum efficiency, and small engines, which lack feasible blade cooling schemes are less efficient.
Many of the schemes for cooling the blades and bearings of turbine engines have involved using various patterns of cooling channels bored into the blades. For example, U.S. Pat. No. 4,522,562, issued Jun. 11, 1985 to Glowacki and Mandet, discloses a cooling scheme in which a turbine disc has a set of channels bored near each of two sides of a disc that conform with the profile of the disc. Each set of channels carries cooling air to superficially cool the disc.
Other attempts to improve turbine operation have been directed to having turbine wheels or rotors that function as both compressors and turbine sections. A prior art example of this can be found in U.S. Pat. No. 4,757,682, issued Jul. 19, 1988, to Bahniuk. This patent discloses a fluid flow that is directed over the compressor section to effect multiple compression stages, with the same air passages being used for both the compression stages and the exhaust air flow. There is no teaching or suggestion of using separate compression intake and exhaust passages that are interleaved in the same rotor or wheel.
A pair of patents, U.S. Pat. No. 3,709,629, issued Jan. 9, 1973, and related U.S. Pat. No. 4,070,824, issued Jul. 19, 1988, both to Traut, disclose a gas turbine having a rotor that serves as both compressor and turbine. The turbine engine utilizes stationary arcuate members located in close proximity to the rotor that direct the flow of combustion products against the rotor blades to cause rotation. The arcuate members also serve to cool the rotor and provide a path for the subsequent exhausting of the combustion flow. These functions are accomplished by a complex ducting arrangement that is completely different than the present invention. The mixing of the flows, sealing problems, and non standard flow passages are problems in the design of this patent, as we well as the preceding patent.
There is not yet a reliable and practical way to cool the turbine of small gas turbine engine. Multiple rotor turbo machines such as engines, turbochargers, refrigeration compressors, and others all suffer from dynamic problems caused by the shaft and rotor system.
Therefore, it is an object of the present invention to provide a practical turbine blade cooling scheme for small gas turbine engines.
It is another object of the present invention to provide a single rotor for a gas turbine engine that has better known and studied flow paths than those of the prior art.
It is still another object of the present invention to provide a rotor for turbomachinery that performs the functions of two rotors in only one rotor, thus eliminating the shaft and the problems it introduces.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, a rotor for use in turbine applications comprises a centrifugal compressor having axially disposed spaced apart fins forming passages, and an axial turbine having hollow turbine blades through which air from the centrifugal compressor flows.
In a further aspect of the present invention, and in accordance with its objects and purposes, a turbine engine comprises a turbine engine housing, the turbine engine housing having a compressed air volute and a exhaust scroll, with a single rotor mounted to a shaft inside the turbine engine housing, the rotor having a centrifugal compressor with axially disposed spaced apart fins forming passages, and an axial turbine having hollow turbine blades interleaved with the fins and through which air from the centrifugal compressor flows. Wherein the centrifugal compressor compresses air into the compressed air volute and heated exhaust air is directed into the hollow turbine blades from the exhaust scroll, causing the shaft to rotate.